A detailed report of these matters reached Tarquin. He was not only furious at the failure of plans from which he had hoped so much, but he was filled with rage at finding the way blocked against secret intrigues; and consequently determined upon open war. He visited the cities of Etruria and appealed for help; in particular, he implored the people of Veii and Tarquinii not to allow one to perish before their eyes who was of the same blood with them, and from being a powerful monarch was now, with his children, homeless and destitute. Others, he said, had been invited from abroad to reign in Rome; he, the king, whilst extending the rule of Rome by a successful war, had been driven out by the infamous conspiracy of his nearest kinsmen. They had no single person amongst them deemed worthy to reign, so they had distributed the kingly authority amongst themselves, and had given his property as plunder to the people, that all might be involved in the crime. He wanted to recover his country and his throne and punish his ungrateful subjects. The Veientines must help him and furnish him with resources, they must set about avenging their own wrongs also, their legions so often cut to pieces, their territory torn from them.

This appeal decided the Veientines, they one and all loudly demanded that their former humiliations should be wiped out and their losses made good, now that they had a Roman to lead them. The people of Tarquinii were won over by the name and nationality of the exile; they were proud of having a countryman as king in Rome. So two armies from these cities followed Tarquin to recover his crown and chastise the Romans. When they had entered the Roman territory the consuls advanced against them; Valerius with the infantry in phalanx formation, [(1)] Brutus reconnoitering in advance with the cavalry. Similarly the enemy's cavalry was in front of his main body, Arruns Tarquin, the king's son, in command; the king himself followed with the legionaries. Whilst still at a distance Arruns distinguished the consul by his escort of lictors; as they drew nearer he clearly recognised Brutus by his features, and in a transport of rage exclaimed, "That is the man who drove us from our country; see him proudly advancing, adorned with our insignia! Ye gods, avengers of kings, aid me!" With these words, he dug spurs into his horse and rode straight at the consul. Brutus saw that he was making for him. It was a point of honour in those days for the leaders to engage in single combat, so he eagerly accepted the challenge, and they charged with such fury, neither of them thinking of protecting himself, if only he could wound his foe, that each drove his spear at the same moment through the other's shield, and they fell dying from their horses, with the spears sticking in them. The rest of the cavalry at once engaged, and not long after the infantry came up. The battle raged with varying fortune, the two armies being fairly matched; the right wing of each was victorious, the left defeated. The Veientes, accustomed to defeat at the hands of the Romans, were scattered in flight, but the Tarquinians, a new foe, not only held their ground, but forced the Romans to give way.